PvP Trade Bets do not work during challenges, only during ranked PvP bouts.

When the first character reaches 50% Health, both players are allowed to place a Trade Bet. Up to 100 of any currency (except Seasonal Currency or GS), up to 10 Crafted Potions/ Runes, or any one consumable (including Elixirs). The bet is revealed to both players, if either declines, the Trade Bet is cancelled. The losing player has their bet traded to the winning player.